First came American Crossroads, Commonsense Ten and their ilk — so-called super PACs set up with unlimited cash that poured millions of dollars into ads benefiting multiple candidates and attacking their opponents.

Now comes the next generation of this new breed of fundraising committees — super PACs created to boost individual presidential candidates, and to strip the bark off their rivals.

They’re already showing signs that they could reshape the presidential campaign landscape in 2012.

A super PAC created to advance Mitt Romney’s campaign for the GOP nomination raised $12.2 million in the first half of the year. One set up to help President Barack Obama spent $97,000 on ads attacking Romney. Supporters of Texas Rep. Ron Paul’s dark horse Republican bid are using a super PAC to pay for $6,000 worth of billboards and print ads ahead of the Ames straw poll. And one of the half-dozen super PACs established to bolster Texas Gov. Rick Perry in his yet-to-be-declared campaign for the GOP nomination is airing ads in Iowa calling him “a better option for president.”

“You can be sure that we haven’t seen the last of these things, whether it’s this cycle or some future cycle, unless the legal climate changes,” said Michael Malbin, executive director of the Campaign Finance Institute, a non-profit, non-partisan group that tracks political fundraising data and trends. “You can’t expect candidates not to take advantage of something like this when their opponents are.”

The creation of super PACs as political advertising vehicles is an outgrowth of the Supreme Court’s pivotal 2010 ruling, Citizens United v. Federal Election Commission, which allowed corporations and unions to spend unlimited cash on campaign ads.

The new crop of candidate-specific super PACs allow deep-pocketed individuals, corporations and unions to write checks far exceeding the maximum amount they can give directly to their preferred candidate ($2,500 per person per election) to groups often run by operatives closely allied with the candidate. The super PACs are legally barred from giving directly to — or coordinating their spending with — their favored candidate. That can curb their effectiveness but also frees the operatives running them to air attack ads and deploy other, far more aggressive tactics than the candidate would want to use.

But the groups also carry risks for the candidates they aim to help. That’s particularly true if the candidates lend their imprimatur to the committees. There’s also potential for friendly fire, which is manifesting itself in a competition to be the super PAC supporting Perry, who is expected to declare his candidacy Saturday. It could hurt both the operatives behind the groups and their favored candidates if the committees get too aggressive with one another or rival candidates, or if they’re accused of playing fast and loose with campaign rules or accepting controversial donations.

Romney, the former Massachusetts governor, got a taste of super PAC backlash late last week, after NBC News reported that a super PAC to which he has close ties, Restore Our Future, accepted $1 million from a company apparently established exclusively to funnel the contribution.

POLITICO subsequently revealed that the source of the cash was a former business associate and longtime political donor to Romney, who declared Monday that “the whole controversy with regards to his contribution sorta disappears when he came forward and said that he was the contributor. … And any issues with regards to his contribution should be directed to him and to the people [running] the PAC.”

The Washington Post, though, editorialized that the “episode does not speak well of Mr. Romney” and urged him to elaborate on what he knew about the donation. The Campaign Legal Center, which had paired with another watchdog group to file complaints over the donation, renewed its call for an investigation of the donation.

“The behavior of super PACs to which presidential candidates are linked will reflect on those candidates, and when that behavior is bad, it should reflect poorly on them,” said Paul Ryan, a lawyer at the nonprofit, nonpartisan center. Although the complaint did not allege wrongdoing by Romney, Ryan added, “Given the seemingly close nexus between Romney, the donor and the political action committee, I don’t think it’s unfair to ask questions to Mr. Romney and to hold him accountable to some extent.”

Super PACs can particularly benefit “candidates who get higher percentages of their money from maximum donations,” Malbin said. His group last month published an analysis showing that Romney’s campaign led the way in that regard in the second quarter, raising 74 percent of its $18.2 million from donors who had already maxed out to Romney’s campaign.

In contrast, Obama’s campaign, which is eclipsing those of all his GOP rivals in fundraising, got only 19 percent of its $49 million from donors who have given the maximum contribution.

GOP finance circles have buzzed about the possibility that wealthy supporters of former Utah Gov. Jon Huntsman, who reportedly has struggled to raise money for his Republican presidential campaign, are planning their own outside group.

There’s no evidence that supporters of Minnesota Rep. Michele Bachmann, whose GOP presidential campaign has raised the highest percentage of funds from small donors, have formed a super PAC to support her.

But in the weeks after Restore Our Future’s pro-Romney mission emerged, supporters of both Paul, who has long relied on small donors, and Perry, whose rise has been fueled by mega donors, registered super PACs with the FEC. In fact, fans of Perry created at least six separate super PACs, and they’re already swiping at one another.

“Many other groups are coming forward to draft and support the governor,” wrote the founders of a new super PAC called Make Us Great Again to would-be donors in a Monday email obtained by the Texas Tribune. “Our advice is to avoid any other group claiming to be ‘the’ pro-Perry independent effort and, when the timing is right, to support Make Us Great Again,” said the email, signed by three Perry loyalists, including Perry’s former chief of staff, Austin lobbyist Mike Toomey.

While Toomey told POLITICO he hasn’t talked to Carney about the group and said “there is no blessing,” he also took an oblique shot at other pro-Perry efforts, saying, “There are all these fundraisers out there trying to make money.”

He added, “I know one major donor was hit up by a [super PAC] that was questionable, and there is a profusion of them out there. A lot of major donors who should be inclined to support the governor if he gets in have got to be confused, so this is an effort to tell people who might want to help if Perry gets in to hold off, and this is the proper forum that will handle their business appropriately.”

Bob Schuman, a California strategist who started another of the pro-Perry super PACs, Americans for Rick Perry, said, “We’re not angling to be the blessed or designated super PAC.”

But his group has retained fundraisers with ties to some of Perry’s biggest donors, last week naming as national finance chairman Nate Crain, a former Dallas County Republican chairman who was a close adviser during Perry’s time as lieutenant governor. It has raised $400,000, primarily from Texans with long records of supporting Perry, such as Dallas billionaire Harold Simmons, who gave $100,000.

“Romney’s got $12 million he wouldn’t have otherwise, and that’s just so far,” Schuman said. “I think all the major candidates, in order to be able to compete financially, are going to need to do some form of that.”

Jobs for Iowa, a super PAC airing ads in that state touting Perry’s presidential mettle, is believed to have been organized by major Perry donors. Yet another pro-Perry super PAC, Veterans for Perry, was created by Dan Shelley, an Austin lobbyist who once served as Perry’s legislative liaison.

Connections to a politician’s inner circle do not necessarily guarantee a candidate’s blessing for a super PAC.

Carney told POLITICO he has discouraged big Perry supporters from giving to Jobs for Iowa, Americans for Rick Perry and Veterans for Rick Perry, though he did not respond this week when asked the same question about Make Us Great Again.

“My advice is to keep your powder dry,” he wrote in an email to POLITICO last week about the other groups, conceding that Perry might offer his support to another super PAC if he runs and decides such an affiliation would be helpful. “We will cross that bridge if we get to it.”

Team Perry’s apparent coolness has done little to dissuade his supporters at the other super PACs.

“If I were him, I think I’d say the same thing,” Schuman said. “And I would probably be inclined, to the extent that I could, to try to get a group going that is led by my own people — people that I’ve known for a long time, that I’ve worked with and trust, people who demonstrate good judgment and know what they’re doing.”

Paul’s campaign, on the other hand, seems inclined to play it safe in the new environment, signaling it intends to keep its distance from all super PACs.

“The expert legal advice I received was that all contact must be avoided, and failing to do so would put Dr. Paul, our campaign and the PAC organizers in jeopardy of civil and criminal penalties,” said Jesse Benton, a Paul campaign spokesman.

But the pro-Paul super PAC Revolution PAC is pushing to raise money from the relatively few donors who have given the maximum to Paul’s campaign. One donor who said he reached his direct contribution limit is tech entrepreneur Scott Banister, who gave the PAC its largest donation — $10,000.

Super PACs are “less valuable to a candidate raising money in small doses,” conceded Banister, who founded an adult social network website. “But, channeling Ron Paul for a moment, [super PAC giving is] still a civil liberty and he would support super PACs, even if they did not raise him a dime and caused him to lose to Romney or someone else.”

Revolution PAC has assembled an advisory board that includes the top lawyer from Paul’s 2008 presidential campaign and the congressman’s former political director. It plans to complement Paul’s official campaign efforts by tailoring its own spending based on public information released by his campaign and by working with the grassroots, said Revolution PAC president Gary Franchi.

“I personally think every candidate should have a super PAC,” he said, “because it just adds to their legitimacy, their prestige and the support that surrounds their effort to run for office.”